Ethyl 4-(1-hydroxy-1-methylethyl)-2-propyl-imidazole-5-carboxylate (formula V) is a key intermediate for the synthesis of olmesartan medoxomil, which can be produced via the reaction of diethyl 2-propyl-imidazole-4,5-dicarboxylate, the raw material, with methylmagnesium bromide, followed by the acidification with saturated ammonium chloride solution (J. Med. Chem. 1996, 39, 323-338).
Moreover, hydroxyl methylated product of olmesartan medoxomil (impurity 1), and hydroxyl eliminated product of olmesartan medoxomil (impurities 2) are the two major impurities in the olmesartan medoxomil as reported by Hedvati Lilach in US2006258727 on Nov. 16, 2006.

The major causes for the formation of impurity 1 and impurity 2 in olmesartan medoxomil are also disclosed by Hedvati Lilach, which are, the reaction of the compound of formula IV with methylmagnesium bromide produces not only the main product as shown by formula V, but also the hydroxyl methylated product (impurity 3) and the hydroxyl eliminated product (impurity 4), compound of formula V containing impurity 3 and impurity 4 will lead to the olmesartan medoxomil containing impurities 1 and 2 after following reactions.

Therefore, there is an urgent need in the art for a novel and more effective process for the preparation of ethyl 4-(1-hydroxy-1-methylethyl)-2-propyl-imidazole-5-carboxylate (formula V), furthermore, high purity ethyl 4-(1-hydroxy-1-methylethyl-2-propyl-imidazole-5-carboxylate (formula V) can be obtained by the provided process so that high purity olmesartan medoxomil can be produced.